dBm是一个表示功率绝对值的值（也可以认为是以1mW功率为基准的一个比值），
计算公式为：dBm=10log（功率值/1mw）
wW=power(10,dBm/10)
W=(power(10,dBm/10))/1000
一、粗略计算方法
这里将dBm转换为W的口算规律是要先记住“1个基准”和“2个原则”：
“1个基准”：30dBm＝1W
“2个原则”：1)＋3dBm，功率乘2倍；－3dBm，功率乘1/2|
举例：33dBm＝30dBm+3dBm＝1W×2=2W
27dBm＝30dBm－3dBm＝1W×1/2=0.5W
2)＋10dBm，功率乘10倍；－10dBm，功率乘1/10
举例：40dBm＝30dBm+10dBm＝1W×10=10W
20dBm＝30dBm－10dBm＝1W×0.1=0.1W
以上可以简单的记作：30是基准，等于1W整，互换不算难，口算可完成。加3乘以2，加10乘以10；减3除以2，减10除以10。
几乎所有整数的dBm都可用以上的“1个基准”和“2个原则”转换为W。
例1：44dBm=?W
44dBm=30dBm+10dBm+10dBm－3dBm－3dBm
=1W×10×10×1/2×1/2
=25W
例2：32dBm=?
32dBm=30dBm+3dBm+3dBm+3dBm+3dBm-10dBm
=1W×2×2×2×2×0.1
=1.6W
计算技巧：+1dBm和+2dBm的计算技巧
+1dBm=+10dBm－3dBm－3dBm－3dBm
=X×10×1/2×1/2×1/2
=X×1.25
+2dBm=－10dBm+3dBm+3dBm+3dBm+3dBmw
=X×0.1×2×2×2×2
=X×1.6
一般来讲，在工程中，dBm和dBm（或dBw和dBw）之间只有加减，没有乘除。而用得最多的是减法：dBm减
dBm 实际上是两个功率相除，信号功率和噪声功率相除就是信噪比（SNR）。dBm加dBm
实际上是两个功率相乘。
一、精确计算方法
计算公式为：dBm=10log（功率值/1mw）
wW=power(10,dBm/10)
W=(power(10,dBm/10))/1000
功率-》dBm的换算
dBmmw dBmmw dBmW dBmW
-100
0.0000000001000000
-50
0.0000100000000000
0
0.001
50
100.000
-990.0000000001258925
-490.0000125892541179
10.001
51125.893
-98
0.0000000001584893
-48
0.0000158489319246
2
0.002
52
158.489
-970.0000000001995262
-470.0000199526231497
30.002
53199.526
-96
0.0000000002511886
-46
0.0000251188643151
4
0.003
54
251.189
-950.0000000003162278
-450.0000316227766017
50.003
55316.228
-94
0.0000000003981072
-44
0.0000398107170553
6
0.004
56
398.107
-930.0000000005011872
-430.0000501187233627
70.005
57501.187
-92
0.0000000006309573
-42
0.0000630957344480
8
0.006
58
630.957
-910.0000000007943282
-410.0000794328234724
90.008
59794.328
-90
0.0000000010000000
-40
0.0001000000000000
10
0.010
60
1000.000
-890.0000000012589254
-390.0001258925411794
110.013
611258.925
-88
0.0000000015848932
-38
0.0001584893192461
12
0.016
62
1584.893
-870.0000000019952623
-370.0001995262314969
130.020
631995.262
-86
0.0000000025118864
-36
0.0002511886431510
14
0.025
64
2511.886
-850.0000000031622777
-350.0003162277660168
150.032
653162.278
-84
0.0000000039810717
-34
0.0003981071705535
16
0.040
66
3981.072
-830.0000000050118723
-330.0005011872336273
170.050
675011.872
-82
0.0000000063095734
-32
0.0006309573444802
18
0.063
68
6309.573
-810.0000000079432823
-310.0007943282347243
190.079
697943.282
-80
0.0000000100000000
-30
0.0010000000000000
20
0.100
70
10000.000
-790.0000000125892541
-290.0012589254117942
210.126
7112589.254
-78
0.0000000158489319
-28
0.0015848931924611
22
0.158
72
15848.932
-770.0000000199526231
-270.0019952623149689
230.200
7319952.623
-76
0.0000000251188643
-26
0.0025118864315096
24
0.251
74
25118.864
-750.0000000316227766
-250.0031622776601684
250.316
7531622.777
-74
0.0000000398107171
-24
0.0039810717055350
26
0.398
76
39810.717
-730.0000000501187234
-230.0050118723362727
270.501
7750118.723
-72
0.0000000630957344
-22
0.0063095734448019
28
0.631
78
63095.734
-710.0000000794328235
-210.0079432823472428
290.794
7979432.823
-70
0.0000001000000000
-20
0.0100000000000000
30
1.000
80
100000.000
-690.0000001258925412
-190.0125892541179417
311.259
81125892.541
-68
0.0000001584893192
-18
0.0158489319246111
32
1.585
82
158489.319
-670.0000001995262315
-170.0199526231496888
331.995
83199526.231
-66
0.0000002511886432
-16
0.0251188643150958
34
2.512
84
251188.643
-650.0000003162277660
-150.0316227766016838
353.162
85316227.766
-64
0.0000003981071706
-14
0.0398107170553497
36
3.981
86
398107.171
-630.0000005011872336
-130.0501187233627272
375.012
87501187.234
-62
0.0000006309573445
-12
0.0630957344480193
38
6.310
88
630957.344
-610.0000007943282347
-110.0794328234724281
397.943
89794328.235
-60
0.0000010000000000
-10
0.1000000000000000
40
10.000
90
1000000.000
-590.0000012589254118
-90.1258925411794170
4112.589
911258925.412
-58
0.0000015848931925
-8
0.1584893192461110
42
15.849
92
1584893.192
-570.0000019952623150
-70.1995262314968880
4319.953
931995262.315
-56
0.0000025118864315
-6
0.2511886431509580
44
25.119
94
2511886.432
-550.0000031622776602
-50.3162277660168380
4531.623
953162277.660
-54
0.0000039810717055
-4
0.3981071705534970
46
39.811
96
3981071.706
-530.0000050118723363
-30.5011872336272720
4750.119
975011872.336
-52
0.0000063095734448
-2
0.6309573444801930
48
63.096
98
6309573.445
-510.0000079432823472
-10.7943282347242810
4979.433
997943282.347
dBm->功率的换算
mw
dBm
mw
dBm
W
dBm
W
dBm
1
0.00
51
17.08
0.1
20.00
42
46.23
2
3.01
52
17.16
0.2
23.01
43
46.33
3
4.77
53
17.24
0.3
24.77
44
46.43
4
6.02
54
17.32
0.4
26.02
45
46.53
5
6.99
55
17.40
0.5
26.99
46
46.63
6
7.78
56
17.48
0.6
27.78
47
46.72
7
8.45
57
17.56
0.7
28.45
48
46.81
8
9.03
58
17.63
0.8
29.03
49
46.90
9
9.54
59
17.71
0.9
29.54
50
46.99
10
10.00
60
17.78
1
30.00
51
47.08
11
10.41
61
17.85
2
33.01
52
47.16
12
10.79
62
17.92
3
34.77
53
47.24
13
11.14
63
17.99
4
36.02
54
47.32
14
11.46
64
18.06
5
36.99
55
47.40
15
11.76
65
18.13
6
37.78
56
47.48
16
12.04
66
18.20
7
38.45
57
47.56
17
12.30
67
18.26
8
39.03
58
47.63
18
12.55
68
18.33
9
39.54
59
47.71
19
12.79
69
18.39
10
40.00
60
47.78
20
13.01
70
18.45
11
40.41
61
47.85
21
13.22
71
18.51
12
40.79
62
47.92
22
13.42
72
18.57
13
41.14
63
47.99
23
13.62
73
18.63
14
41.46
64
48.06
24
13.80
74
18.69
15
41.76
65
48.13
25
13.98
75
18.75
16
42.04
66
48.20
26
14.15
76
18.81
17
42.30
67
48.26
27
14.31
77
18.86
18
42.55
68
48.33
28
14.47
78
18.92
19
42.79
69
48.39
29
14.62
79
18.98
20
43.01
70
48.45
30
14.77
80
19.03
21
43.22
71
48.51
31
14.91
81
19.08
22
43.42
72
48.57
32
15.05
82
19.14
23
43.62
73
48.63
33
15.19
83
19.19
24
43.80
74
48.69
34
15.31
84
19.24
25
43.98
75
48.75
35
15.44
85
19.29
26
44.15
76
48.81
36
15.56
86
19.34
27
44.31
77
48.86
37
15.68
87
19.40
28
44.47
78
48.92
38
15.80
88
19.44
29
44.62
79
48.98
39
15.91
89
19.49
30
44.77
80
49.03
40
16.02
90
19.54
31
44.91
81
49.08
41
16.13
91
19.59
32
45.05
82
49.14
42
16.23
92
19.64
33
45.19
83
49.19
43
16.33
93
19.68
34
45.31
84
49.24
44
16.43
94
19.73
35
45.44
85
49.29
45
16.53
95
19.78
36
45.56
86
49.34
46
16.63
96
19.82
37
45.68
87
49.40
47
16.72
97
19.87
38
45.80
88
49.44
48
16.81
98
19.91
39
45.91
89
49.49
49
16.90
99
19.96
40
46.02
90
49.54
50
16.99
100
20.00
41
46.13
91
49.59